1. Technical Field
This disclosure relates to fault detection circuits, and more particularly, to an apparatus and method for electronic tripping systems and methods that minimize arc energy for safety during maintenance.
2. Description of the Related Art
Proper system maintenance and safety are the constant concern of electrical equipment manufacturers and servicers. In particular, arc fault is one area where manufacturers are looking for ways to make their equipment inherently safer to users who maintain electrical systems. Under normal operating conditions, electrical equipment is enclosed by a “dead-front” enclosure to protect people from accidental contact with energized parts, and to contain any gases or exhaust that may occur during a tripping operation.
In a power or main circuit breaker system within an electric distribution system, a main circuit breaker or power circuit breaker is connected between a power source terminal and a plurality of branch load circuits. Additionally, feeder circuits may be coupled in the electrical distribution system. Typically, each branch or feeder circuit is protected by a circuit breaker or fuse connected between the power source and the load, such as an induction motor or the like. In operation, the main circuit breaker typically is configured to operate or trip at a higher power setting current pass through, then the branch circuit breakers or feeder circuit breakers.
If a short circuit or other reason to cut power to a specific load circuit occurs, the feeder or branch circuit breaker is configured to open before the time delay designed into the main circuit breaker. In such operation, only the affected load is cut from the electrical distribution system with the remaining load circuits continuing to be connected to the electrical distribution system.
In the event that personnel have to enter the area where a short circuit exists or work on an electrical machine is needed, there is a possibility of arc flash from the surrounding “live” circuitry. An arc flash hazard is defined as a dangerous condition associated with the release of energy caused by an electrical arc.
An electrical arc operates at temperatures of several thousand degrees Celsius and creates a pressure wave, not unlike an explosion, causing metal particles, equipment parts and other loose items to be expelled from the electrical arc flash area in addition to the expulsion of hot, ionized gases. If a human being is in the vicinity of such arc flash hazard, bodily injury, including death, can result.
In addition to warnings, the setting of boundaries that mark where personnel may not enter without wearing appropriate protective gear/clothing is used to designate the arc flash hazard area. Before personnel can approach electrical gear within such designated flash protection boundary, the personnel would be required to wear fire-retardant arc flash suits which are uncomfortable, expensive and limit the personnel's ability to work on the electrical equipment. Another alternative available to working in the arc flash hazard protected area is to open the main circuit breaker which would cut power to all of the branch and feeder circuits protected by such main circuit breaker. Such procedure is expensive and inefficient.